The present invention relates to a tool cooling device for machine tools, such as, NC milling machines of the type equipped with an automatic tool changer (hereinafter referred to as machining centers).
For instance, as is well known in the art, a machining center includes many different types of tools (cutters) accommodated in a tool magazine so that the desired tool is selected and changed automatically to machine a work, and a marked tendency to machine non-ferrous material such as aluminum or plastic material is seen lately. As a result, the machine tool is required to perform cutting at very high speeds with the resulting remarkable increase in the spindle speed and increase in the heating of tools. Therefore, the conventional practice of supplying a cutting oil to the outside of the tool cannot cool the tool satisfactorily with the resulting considerable deterioration of the tool cutting efficiency.
In an attempt to overcome these deficiencies, for example, recently a drill is formed with a hole in the lengthwise direction thereof (hereinafter referred to as an oil hole) so that a cooling fluid such as cutting oil is supplied into the oil hole thus cooling the tool and also forcibly removing the chip with the fluid pressure and thereby reducing the cutting resistance.
In order to supply the cooling fluid to the tool having such oil hole, the usual practice is to force the cooling fluid into the oil hole through a pipe having its one end connected to a cooling fluid pump and other end coupled to the tool holder. However, the tool magazine accommodates tools with oil holes and those having no oil hole as desired and in a suitable manner so that only when the tool having an oil hole is engaged with the spindle, the pipe is connected to the tool holder and the cooling fluid is supplied into the oil hole. In other words, there is a disadvantage that it takes a great deal of trouble and much time is required for making the necessary arrangements since the pipe must be connected or disconnected depending on the tool engaged with the spindle.